108 THE SHORTER SCIENTIFIC PAPERS 



3. Comparative Correlation of Length and Diameter 



In view of the results obtained in a consideration of the 

 variability, it will be of some interest to ascertain whether 

 the inbred zygospores produced by lateral conjugation 

 will be more or less correlated than the cross bred zygo- 

 spores produced by scalariform conjugation so far as 

 length and diameter are concerned. 



The value of perfect correlation as measured by the 

 constant (r) is unity, while absence of correlation allows 

 the value to become zero. Length is taken as the subject 

 class {y) and diameter {x) as the relative class in the 

 accompanying tables. 



While one might infer that the longer a zygospore the 

 greater the diameter, such a condition is not apparent by 

 mere inspection of the tables in either case. Consequently 

 on solving the equations we are prepared to find that the 

 coefficients have an extremely low value in each group. 



Lateral Conjugation r =^ .1894 zi= .0460 



Scalariform Conjugation r = .0934 z±z .0473 



Although in lateral conjugation the value is more than 

 four times the probable error, one is scarcely prepared to 

 state that there is greater correlation between characters 

 in close breeding than in cross breeding on the basis of 

 the data noted above. When considered with the results 

 presented in Table XII, the conclusion seems fully estab- 

 lished, however. 



4. Comparative Size of Zygospores 



The term "size" as noted in the subsequent discussion 

 is open to various interpretations dependent as to whether 

 length, diameter or volume is being considered, a condi- 

 tion which to some extent complicates the interpretation 

 of size characters among multicellular organisms which 

 are in general dependent on the number rather than the 

 dimensions of the component cells. 



Those zygospores produced by lateral conjugation 

 (close bred), so far as the present material is concerned, 

 have an average length considerably exceeding those 

 produced by scalariform conjugation (cross bred) while 



